Fan housing for feeding air to a ventilation system

Abstract

 The present invention relates to a fan housing for feeding air via an outlet (14) to a ventilation system. The fan housing comprises a radial impeller (16) rotatably mounted to a shaft which wheel has at least one centrally arranged inlet (17) and a number of impeller blades (18). Furthermore, there is a wall (20) being substantially parallel to the rotational axis which wall is curved with a monotonous increasing radius in relation to said shaft, between a first end edge (21) at a certain distance from said impeller and a second end edge (22) at a larger distance from said impeller. An imagined, straight line (23) between the two end edges (21, 22) extends through the impeller (16).

Description

TECHNICAL FIELD

[0001] The present invention relates to a fan housing for feeding air to a ventilation system, comprising a radial impeller rotatably mounted to a shaft which wheel has one centrally arranged inlet and a number of impeller blades and having a wall being substantially parallel to the rotational shaft which wall is curved with a monotonous increasing radius in relation to said shaft, between a first end edge at a certain distance from said impeller and a second end edge at a larger distance from said impeller.

BACKGROUND OF THE INVENTION

[0002] Fans for ventilation systems are normally provided with a shell shaped fan housing, which cooperates with the impeller to provide a high efficiency, i.e., a high total pressure (static pressure + dynamic pressure) in relation to the driving force added. As there is, in most cases no room for a accurate installation, where the uneven speed distribution in the fan outlet and the dynamic pressure is taken care off, pressure losses are obtained. Furthermore, fans creates a high noise level, which is transported away in the ventilation system if no noise suppressing measures are taken. A normal means is to place one or more silencer in the canal system before and after the fan. Silencing measures are space demanding, lead to an increased fall of pressure in the ventilation system, and lead to increased investment costs.

[0003] A substantial part of the noise created relates to the pulses of pressure created when the impeller blades passes the first end edge of the wall. These pressure pulses are acoustically intensified by the funnel shaped outlet and are transported further on in the ventilation system if no necessary sound suppressing is made.

THE TECHNICAL PROBLEM

[0004] The object of the present invention is to obtain a fan housing for a ventilation system which creates less pressure losses and which creates less noise than a corresponding, known fan housing.

THE SOLUTION

[0005] To achieve this object, the invention is characterized in that an imagined straight line between the two end edges extends through the impeller. By means of this design of the curved wall, the pressure pulses from the impeller blades will be reduced to a considerable extent. Furthermore, the fan housing lacks the funnel shaped outlet.

DESCRIPTION OF THE DRAWINGS

[0006] The invention will be described in the following with reference to the embodying example given in the attached drawings, in which

FIG. 1

shows a schematic side view of a fan housing designed in accordance with the invention, having one sidewall removed.

FIG. 2

is an end view of the fan housing according to FIG. 1

DESCRIPTION OF THE EMBODYING EXAMPLE

[0007] The fan housing shown in the drawing is intended to feed air via an outlet 14 defined by four walls 10 to 13, to a ventilation system not shown. The fan housing comprises a double-sided radially working impeller 16 being rotatable driven by a shaft 15 which wheel has two central inlets 17, and a number of impeller blades 18 on each side of a centre wall 19. Furthermore, the fan housing comprises a wall 20 being substantially parallel to the rotational axis, which wall is curved between a first end edge 21 and a second end edge 22.

[0008] The bend of the wall is done in such a way that the wall has a monotonous increasing radius distance in relation to the shaft 15. Thus the distance between the outer radius of the impeller and the first end edge 21 is less than the corresponding distance to the other end edge 22.

[0009] If one connects the two end edges 21, 22 with an imagined, straight line 23 this line will extend through the impeller 16. This means that the wall 20 is truncated in comparison with conventional shell shaped fan housings which generally extend from one side of the outlet towards the outer radius of the impeller and from there arcshaped with a monotonous increasing radius towards the opposite side of the outlet.

[0010] The straight line 23 passes through the impeller in the vicinity of the rotational axis 15, between the wall 20 and the outlet 14 ofthe fan housing. The wall is provided with a silencing material 24 on the on the side facing away from the impeller 16.

[0011] According to a variation of the embodiment of the invention the wall is totally formed by a mould casting of the silencing material, which can be made of stone wool, glass wool, or of a foamed plastic, e g., polyurethane. The wall surface is preferably protected by means of a perforated steel sheet (not shown in the drawing), whereby the polymer material forms a supporting body of the perforated steel sheet. As the wall 20 is hereby formed in a rapid and rational way the manufacturing costs of the fan housing are reduced. The sound waves passes through the perforated steel sheet and are suppressed in the material.

[0012] As the inner end edge of the wall 20 is not present in the neighbourhood of the impeller 16, only a fraction of the pulsing sound is created which is created by and in a conventional fan housing. Furthermore, there is no directed, acoustic intensification of the noise in the direction of the ventilation system. The turbulent sound which is created by the influence of the impeller blades on the air, will be suppressed to a great extent by means of the silencing material.

[0013] As the outlet 14 is larger than those of corresponding conventional shell shaped fan housings, a lower exit speed is obtained which leads to a larger proportion of static pressure and lower pressure losses. It has now surprisingly been shown that using the fan housing of the invention a higher flow at lower pressures are obtained than of the corresponding conventional fan housings. By means of the low noise level at the fan housing of the present invention the ventilation channels can be made short and need not comprise any silencing element. Thus the pressure fall is reduced in the ventilation system and one needs not to dimension the fans/fan housing to resist high working pressures.

[0014] The invention will not be restricted to the embodying examples shown above but several variants can be imagined within the frame of the following claims. For example the wall 20 can be designed in several ways within the frame of the invention.

Claims

1. Fan housing for feeding air via an outlet (14) to a ventilation system, comprising a radial impeller (16) rotatably mounted to a shaft which wheel has at least one centrally arranged inlet (17) and a number of impeller blades (18) and having a wall (20) being substantially parallel to the rotational axis which wall is curved with a monotonous increasing radius in relation to said shaft, between a first end edge (21) at a certain distance from said impeller and a second end edge (22) at a larger distance from said impeller, characterized in that an imagined, straight line (23) between the two end edges (21, 22) extends through the impeller (16).

2. Fan housing according to claim 1, characterized in that the straight line (23) passes through the impeller (16) in the vicinity of the rotational axis (15) and that the line is situated between the wall (20) and the outlet (14) ofthe fan housing.

3. Fan housing according to claim 1 or 2, characterized in that the wall (20), on the side facing away from the impeller (16) is provided with a silencing material (24).

4. Fan housing according to claims 1 or 2, characterized in that the wall (20) is formed by a material (24) having silencing properties.

5. Fan housing according to claim 4, characterized in that the wall (20) is formed by mould casting of the silencing material, which may consist of stone wool, glass wool, or of a foamed plastic, e.g., polyurethane.

6. Fan housing according to any of the preceding claims, characterized in that the wall (20) is composed of a perforated steel sheet and supporting body of a silencing material.

Drawing